If your Windows 7 partition seems to be updating itself after you’ve booted into it, there’s a reason why.

Per ZDNet, as Microsoft marches toward its early April 2013 end of free support deadline for Windows 7, the company is planning to update automatically some of those who still have yet to install the first (and seemingly only) Service Pack for the operating system.

As announced on March 18 via its “Blogging Windows” blog, Microsoft plans to begin rolling out Windows 7 SP1 automatically, via Windows Update to Windows 7 users who still are running the release-to-manufacturing (RTM) version without SP1 installed. This process will begin on March 19.

From the blog post:

“Starting tomorrow, the installation will be fully automatic with no user action required for those who already have Automatic Update enabled. SP1 will be released gradually over the coming weeks to all customers on the RTM version of Windows 7. The service pack will take slightly longer to install compared to other updates. To ensure Service Pack 1 is installed without issue, customers should check for sufficient free disk space and that AC power is present on a laptop. If additional space needs to be created, we recommend using the Disk Cleanup tool to delete some files so that the service pack will install. If the service pack installation is interrupted, it will reattempt to install automatically after the next restart.”

This automatic update will be applied only to Windows 7 consumer PCs that are not managed via other Microsoft management tools like System Center Configuration Manager or Windows Server Update Services (WSUS), the post noted. Some admins have chosen to temporarily block their users from getting SP1 until they’ve tested it to their satisfaction. Those in that category won’t be getting SP1 pushed to them starting tomorrow.

Windows 7 RTM, with no service pack installed, will no longer be supported as of April 9, 2013, according to a February 14 post on the Microsoft Springboard Series blog. Support for specific Windows releases ends 24 months after the release of a new Service Pack, and Windows 7 SP1 was released in February 2011.

Windows 7 SP1 mainstream (free) support continues until January 13, 2015. Extended (paid) support for Windows 7 SP1 is available until January 14, 2020. (Microsoft continues to provide security updates for free during the Extended support phase of a product.)

Microsoft made available last week a Windows 7 hotfix rollup that includes 90 previously released hotfixes.

So, if you’ve been lax with the “Windows Update” feature on your Windows 7 partition, it might just do it for you.